A Certain Scientific Railgun is a Japanese manga series written by Kazuma Kamachi and illustrated by Motoi Fuyukawa, which began serialization in the April 2007 issue of ASCII Media Works' Dengeki Daioh magazine. The manga is a spin-off of Kamachi's A Certain Magical Index light novel series, taking place before and during the events of the main story. Seven Seas Entertainment began publishing the series in North America in June 2011. An anime television series adaptation by J.C.Staff aired in Japan between October 2009 and March 2010, followed by an original video animation released in October 2010. A second season titled A Certain Scientific Railgun S aired between April and September 2013. A spin-off manga series titled A Certain Scientific Railgun: Astral Buddy began serialization in Dengeki Daioh from April 2017 to July 2020. A third season titled A Certain Scientific Railgun T aired between January and September 2020.

Monthly Comic Dengeki Daioh is a Japanese shōnen manga magazine published by ASCII Media Works under the Dengeki brand. Many manga serialized in Dengeki Daioh were later published in tankōbon volumes under ASCII Media Works' Dengeki Comics imprint. The magazine is sold every month on the 27th. A yonkoma section of Dengeki Daioh called Dengeki Yonkoma Daioh (電撃4コマ大王) features various omake strips of the manga series published in it. The format is typically a normal drawing on the right side featuring one or sometimes more characters, and a vertical four panel strip on the left featuring characters from the associated series in super deformed form. Two special editions of the magazine called Dengeki Moeoh and Dengeki Daioh Genesis are sold bimonthly and quarterly, respectively.